RFR(T/S): 8236975 "compiler/graalunit tests fails with --illegal-access=deny"

[Ekaterina Pavlova]

Hello,

Please review the changes which allow to specify additional VM flags to be used to run particular Graal unit tests.
The fix makes Graal unit tests which previously failed with --illegal-access=deny to pass now.


       JBS: https://bugs.openjdk.java.net/browse/JDK-8206113
    webrev: http://cr.openjdk.java.net/~epavlova//8236975/webrev.00/index.html
   testing: run graalunit tests with and without "--illegal-access=deny" flag in mach5


thanks,
-katya